The human immunodeficiency virus (HIV-1) is a complex retrovirus with regard to its genome architecture and gene expression. The human retroviruses including HIV-1 code for specific viral proteins which regulate gene expression at the transcriptional and post-transcriptional levels. The transactivator of HIV transcription (Tat) is one such protein, which has been the subject of intense investigation. The first objective of this pilot project s the development and application lf RNA viral vectors to study the molecular mechanism of Tat protein function. RNA viral vectors represent a new generation of biomolecules which are being exploited to deliver specific RNA viral molecules into cells. The second objective of this pilot project involves the construction of RNA vectors carrying TAT specific antisense and decoy RNA sequences of HIV-1. The constructs will be used to inhibit the HIV-1 gene expression in tissue culture systems. These two objectives are interlinked, and involve very similar experimental strategies.